From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754242AbaEFT1F (ORCPT ); Tue, 6 May 2014 15:27:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:12774 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751459AbaEFT1C (ORCPT ); Tue, 6 May 2014 15:27:02 -0400 Date: Tue, 6 May 2014 21:26:41 +0200 From: Oleg Nesterov To: Denys Vlasenko Cc: linux-kernel@vger.kernel.org, Jim Keniston , Masami Hiramatsu , Srikar Dronamraju , Ingo Molnar Subject: Re: [PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them Message-ID: <20140506192641.GA12481@redhat.com> References: <1399314247-7368-1-git-send-email-dvlasenk@redhat.com> <20140505194100.GA26916@redhat.com> <5369156C.4000602@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5369156C.4000602@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Firstly, let me remind that my understanding of low lovel hardware details is very limited. On 05/06, Denys Vlasenko wrote: > > Oleg, can you clear for me the following - > > If the probed instruction triggers an "illegal insn" or "privileged insn" > CPU exception - are we completely fine? Yes I think we are fine. I assume that, say, do_debug() won't be called in this case, and do_invalid_op()->do_trap() should trigger arch_uprobe_xol_was_trapped() logic. Well, actually we are not 100% fine because si_addr can be wrong. But this is not invalid_op-specific, we need to fix this anyway and the fix is simple. I do not want to discuss this now, but I am going to make another series later which adds something like uprobe_instruction_pointer(regs). It can (should) be used by DO_ERROR_INFO() (perhaps by something else, not sure about math_error()) _and_ by show_unhandled_signals users (actually the main reason to me). The only problem is that this code should be cleanuped first. In fact I was thinking about this change from the very beginning of the recent fixes, the "wrong" ip reported by do_general_protection() greatly complicated the investigation of that problem. But I need to take a rest of uprobes ;) Oleg.